1. Field of the Invention
This invention relates to an exposure control device, and more particularly to an electric circuit for controlling exposure time in an automatic exposure control device for a photographic camer in which scene brightness information is converted to exposure time by way of a log conversion diode.
2. Description of the Prior Art
In the conventional analogue type exposure control circuit, scene brightness information from a light measuring circuit is log-compressed and the log-compressed information is log-expanded by use of the diode characteristics of a diode. In the analogue type exposure control circuit, the accuracy is unsatisfactorily low because of fluctuation in the various properties of the circuit elements. In the conventional digital type exposure control circuit, the scene brightness information is memorized after being log-compressed. In this case, the digital value memorized must be once converted to an analogue value before being log-expanded. Further, in the digital type control, the accuracy is markedly lowered when the shutter speed is low. In addition, the digital control circuit employs a considerable number of elements.